Gear



Nov. 27, 1934.

E. WILDHABER GEAR Filed 001;. 29, 1931 IIIIIIK I INVENTOR Emma! 7141 Patented Nov. 27, 1934 UNITED STATES GEAR Ernest Wildhaber, Rochester, N. Y., assignor to Gleason Works, Rochester, N. Y., a corporation of New York Application October 29, 1931, Serial No. 571,848 7,

13 Claims. (Cl. 74 4ss) The present invention relates to gears and particularly to gearing such as may be employed in the steering mechanism of automotive vehicles. The primary purpose of the present invention is .5 to provide an improved form of steering mechanism in which the gears will have improved tooth contact and less frictional loss and less wear than in the usual worm drive. A further object of the invention is to provide a steering mech- 1o anism which may be produced simply and inexpensively on existing gear cutting machinery. A still further object of the invention is to provide a steering mechanism which will be more compact than steering mechanisms heretofore used.

Heretofore, the use of longitudinally curved tooth gears has been confined to rear axle and overhead cam-shaft drives. In rear axle drives, particularly, such gears excel other types of gearing because of their longer life and smooth runnin qualities and for these reasons they have practically displaced other types of rear axle drives entirely. It is the purpose of the present invention to enable the advantages of such gearing to be realized in the steering gear field.

The gearing of the present invention comprises a longitudinally curved tooth crown gear and a cylindrical pinion generated to mesh with said crown gear and run in offset position therewith. Both the crown gear and the pinion can be cut with standard facemill gear cutters such as are now ordinarily .used in the cutting of .spiral bevel gearsand they may be produced with the speed of production which characterizes the operation of such cutters. The crown gear will preferably be out without generating roll by simply feeding the cutter into depth while'it is rotating'in engagement with the blank, the blank being held stationary during the feed movement and being indexed only after .each tooth space has been completed. The pinion will be generated to mesh correctly with the crown gear by rotating the cutter in engagement with the pinion blank while simultaneously producing a relative rolling movement between the cutter and pinion blank as though the blank were rolling with the mating crown gear. In its rolling generating movement, the axis of the pinion blank will be maintained offset from and perpendicular to :the axis of the crown gear, that is, in a position corresponding to the position in which the pinion is to run when in mesh with the crown gear. If it be desired to out two sides of a pinion tooth at once, the blades of the pinion cutter may be adjusted in the cutv55 .ter head so that the cutter will be complemental to thegearcutter and its blades straddle a tooth of the pinion blank to cut simultaneously opposite side faces of such tooth.

Both the crown gear and. pinion of my improved pair can be out on existing gear cutting E3 machinery. The crown gear may be cut on machines of the type now used for roughing spiral bevel ring gears, as no gene-rating roll is required. Such machines are comparatively simple and rigid because of the absence .of a generating roll to and the mechanism for producingthe same. The pinion can be cut on Gleason hypoid generators, the cutter and blank being adjusted relative to one another so that the axis of the cradle represents the axis of the crown gear.

One of the features of the present invention is the saving in the time of production of the gear or larger member of a steering pair. Ordinarily thelar-ger gear is not a complete gear but only a segment. The correct method of producing a gearof an ordinary worm andworm wheel steering mechanism is to hob it with a hob corresponding to the worm but in a bobbing process, the blank 'must be rotated round and round upon its axis until the hob has been fed to a full depth. Thus as much time is taken in the hobbing of a segment having only a few teeth as is required in the cutting of a complete gear, the hob simply cutting air mos-t of the time. To avoid this great loss of time, it is the practice of some gear cutting plants to cut-the gear or wheel with a :milling cutter in an intermittentindexing operation, but this can be done only by sacrificing accuracy, for awheel so cut will not be truly conjugate to the worm. In my improved pair, the crown gear may be cut in an intermittent indexing operation so that when all of the teeth have' been out, the segment is finished and there will be no loss of cutting time whatever. As the pinion is generated conjugate to the crown gear, the two will run correctly together.

Another feature of a steering gear pair out according to the present invention is the flexibility of control over the tooth surface bearing. In an ordinary worm and worm wheel pair, the worm is completely conjugate to the wheel, no adjust-' ment is possible and moreover, there is consid-' erable frictional resistance to turning. In the crown gear and cylindrical pinion pair :of the present invention, any desired amount of tooth us bearing can be obtained by suitably selecting the radii of longitudinal tooth curvatures'of gear and pinion. Thus the gears will be capable of adjustment in mesh and steering will also be made easier.

Cir.

The principal'objects of the present invention have already been described. Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawing:

Figure 1 is a view, slightly in perspective, of a steering gear clrivecut according to the present invention;

Figure 2 is a view at right angles to that of Figure 1, the gear being shown in section;

Figure 3 is a fragmentary sectional view of the crown gear taken in a plane normal to the crown gear teeth;

Figure 4 is a diagrammatic view illustrating the method of producing the pinion or smaller member of the pair;

Figure 5 is a diagrammatic'view illustrating the method of producing the crown gear;

.which may exist between the cutters employed inproducing the gear and pinion, respectively, when it is desired to out both members of. the pair spread-blade, that is, two tooth sides simultaneously; and

Figure '7. is'a corresponding view showing a different relationship between the two cutters, as where it is-desired to localize the tooth bearing.

10 designates the crown gear of the pair, a segment. This gear is provided with teeth 11 which are curved longitudinally along circular arcs. The sides of the teeth are preferably made straight in profile being portions of conical surfaces. Because of the difierence in the tooth action' when. steering in opposite directions, the pressure angles of the two sides of the teeth 11 of the crown gear are different. As shown, the pressure angle a of the concave sides 12 of the gear teeth is larger than the pressure angle a of the convex sides 13 of the gear teeth.

The pinion. 14 for a steering mechanism will have a very small number of teeth. The pinion shown in the drawing has only one tooth, resembling in outwardappearance very-closely a cylindrical worm. The profiles of this tooth 111 5 are, however, generated to mesh correctly those of the gear teeth. The pinion is mounted to mesh with the gear with its axis 16 at right angles to and offset from the axis 17 of the crown,

gear. The tooth spaces of the crown gear are of substantially the'same height throughout their length and the teeth are likewise of substantially uniform height from end to end. The pinion is cylindrical,

In cutting the crown gear 10, a face mill gear cutter 20 will. preferably be employed. This cutter may be of standard construction such as described in U. S. Patent No. 1,236,834 issued to James E. GleasonAugust 14, 1917. For the purpose of clearance and to avoid mutilation of the gear teeth, the cutter may be tipped as shown in Figure 5 so that its axis 21 is inclined to the pitch plane 22 of the-crown gear. The pressure angles of the opposite side cutting edges 23 and 24 of the cutting blades will be selected so that when the cutter is rotated in engagement with the gear blank, tooth surfaces will be cut in the gear blank which will have the desired difference in pressure angle on opposite sides of the gear afdepthwise feed movement is produced between the cutter and blank to feed the cutter into the blank to cut tooth spaces of the correct depth.

' In this feed movement, the blank will preferably be held stationary. The rotating cutter thus sweeps out longitudinally curved tooth surfaces on the blank which are of conical formation and may be a face mill gear cutter of standard construction. The cutter is positioned with reference to the cylindrical pinion blank 14 so that it represents a tooth surface or tooth surfaces of j the mating crown gear. Its axis 31 may be inclined to the pitch plane of the crown gear, if desired, at a different angle from the inclination of the axis 21 of the cutter 20 to that plane, when it is desired to have a tooth bearing on the gear which does not extend for the full length of the tooth surface. In the generation of the-pinion 14, the cutter 30 is rotated on its axis 31 in engagement with the blank and simultaneously a relative rolling movement is produced between the cutter and blank as though the blank were meshing with the crown gear 10. Preferably this rolling movement will be accomplished by rotating the pinion blank 14 on its axis 16 and simultaneously producing a relative movement between the pinion blankand the cutter 30 about an axis 17' representing the axis of the crown gear which is shown in dotted lines at 10'. The axis 16 of the blank is positioned and maintained during the generating operation with its axis perpendicular to the axis 1'7 of the generating crown gear and with its axis offset the same amount from the axis 17' of the crown gear as it is offset when in mesh with the mating crown gear. If the crown gear is cut, as is preferred, in an intermittent indexing operation, the pinion will be cut in the same manner. Of course, if the pinion has, as shown, a single tooth, when this tooth has been completely generated, the operation of producing the pinion will have been completed.

The pinion tooth surfaces may be cut one side at a time although it is possible'to out two sides simultaneously. pinion are to be out two sides at a time, that is, spread-blade, the cuttersused for'cutting the gear and pinion should be complementary. Thus in Figure 6, 40 represents the cutter which is cutter. The cutting blades42 of the gear cutter If the tooth surfaces of the' 40 will cut twosides of a tooth space of the crown gear simultaneously'while the cutting blades 43 and 44 of the pinion cutter 41 will straddle the teeth of the pinion and cut opposite sides of the same teeth simultaneously. The blades 43 and 44 of the pinion cutter represent exactly, therefore, adjacent sides of a tooth space of the crown pitch plane 22 of the crown gear so as to avoid mutilation of the crown gear teeth. To produce teeth in the pinion exactly complementary to the tooth spaces of the crown gear, the pinion cutter 41 shouldhe arranged with reference to the pitch plane 22 of the crown gear so that the tooth surfaces swept out by the cutting blades 43 and 44 of -the pinion cutter will exactly match those' As already noted, theres swept out by the cutting bladesof the gear cutter, that is, so that the axes 45 and 46 of the two cutters when referred to the pitch plane 22 are in alignment.

In Figure 7, I have indicated diagrammatically how the complementary gear and pinion cutters may be positioned where it is desired to out tooth surfaces on the gear and pinion having a localized tooth bearing, that is, a tooth bearing which does not extend for the full length of the tooth face. 50 represents the gear cutter having an axis at 51 and cutting blades 52. This is preferably positioned, as before, with its axis 51 inclined to the pitch plane 22 of the crown gear to give the necessary clearance. This cutter 50 will cut opposite sides of a'tooth space of the crown gear simultaneously. The pinion may be cut with a cutter 55 whose cutting blades 56 and 57 are complementary to the cutting blades 52 of the cutter 50, but in cutting the pinion the axis 58 of this cutter will be inclined to the pitch plane 22 of the crown gear at an angle different from the angle which the axis 51 of the cutter 50 makes with said plane during the cutting of the gear. By positioning the two outters so that they are inclined at different angles to the pitch plane of the crown gear, when cutting the gear and pinion, respectively, surfaces of slightly different lengthwise curvature will be swept out on the crown gear and pinion, respectively, and the tooth surfaces of the two members will consequently not match each other exactly along their full length so that a localization of tooth bearing will be obtained with the result that considerable adjustment of the gears in mesh will be possible.

In cutting the crown gear, the radius of the cutter and the position of the crown gear teeth will preferably be selected so that contact between the tooth surfaces of the crown gear and pinion will take place substantially in a plane containing the pinion axis 16, that is, substantially along the line of tangency between the pitch cylinder of the pinion and the pitch plane of the crown gear.

In use, the pinion 14 is secured to the steering column of the automobile while the crown gear segment 10 is secured to the mechanism operating the wheels so that when the pinion is rotated in one direction or the other, the wheels will be turned.

The gearing of the present invention comprises a much more compact steering mechanism than has heretofore been used for the reason that the drive member of the new pair will be on the side of the segment instead of on the periphery thereof as in the case with an ordinary worm and worm wheel steering mechanism.

While the invention has particular application to steering mechanisms, it is not restricted to this use as gearing of the character described may be used in rear axle drives or in drives of various other types where it is desired to transmit motion between two shafts at right angles to one another.

In general it may be said that this application is intended to cover any variations, uses, or adaptations of the invention, following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the gear art and as may be applied to the essential features hereinbefore set forth and as fall within the limits of the invention or the scope of the appended claims.

Having described my invention, what I claimis:

1. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of said crown gearand disposed at right angles to a plane containing the .axiso'f the crown gear, both the crown gear and pinion having longitudinally curved tooth surfaces, the crown gear having tooth surfaces of uniform pressure angle from end to end and the tooth surfaces of the pinion being molded-generated conjugate toxthose .of the crown gear. I

2. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said acrown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, both the crown gear and pinion :having longitudinally curved tooth surfaces, the crown gear having tooth surfaces of uniform pressure angle from end to end but of different pressure angle on -op-- posite sides, the 'concavesides of the teeth being of the larger pressure angle, and the pinion having tooth surfaces molded-generated conjugate to those of the crown gear.

3. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, both the crown gear and pinion having longitudinally curved tooth surfaces, the crown gear .having tooth surfaces of straight profile and uniform pressure angle from end to end but of different pressure angle on oppositesideathe concavesides of the teeth being of the larger pressure angle, and the pinion having tooth surfaces moldedgenerated conjugate to .thoseof the crown gear.

4. A pair of gears-comprising-a crown gear and a pinion, said pinion :meshing with said crown gear with its axis onset from the axis ofythe crown gear and disposed 'at .right angles to a plane containing the .axis'of thecrown'gear both said crown gear and pinion having toothed surfaces curved longitudinally along circular arcs, said crown gear having tooth surfaces of uniform pressure angle from end to end and said pinion having tooth surfaces molded-generated conjugate to those of the crown gear.

5. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of said crown gear and disposed at right angles to a plane containing the axis of the crown gear, both said crown gear and pinion having tooth surfaces curved longitudinally along circular arcs, said crown gear having tooth surfaces of uniform pressure angle from end to end but of different pressure angle at opposite sides and said pinion having tooth surfaces molded-generated conjugate to those of the crown gear.

6. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, both said crown gear and pinion having tooth surfaces curved longitudinally along circular arcs, said crown gear having tooth surfaces of straight profile and of uniform pressure angle from end to end and said pinion having tooth surfaces molded-generated conjugate to those of the crown gear.

'7. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axisof the crown gear,. both said crown gear and pinion having tooth surfaces curved longitudinally along circular arcs, said crown gear. having toothsurfaoes of straight profile-and, uniform pressure angle from end to'endbut of different pressure angle on opposite sides of the teeth and said pinion having tooth surfaces molded-generatedconjugate to those of thecrowngean. A

8. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, both said crown gear and pinion having tooth surfaces curved longitudinally along circular arcs, the tooth' surfaces of the pinionbeing curved along slightly different circular arcs from the mating tooth surfaces of the crown gear, said crown gear having tooth surfaces of uniform pressure angle from end to end and said pinion having tooth surfaces moldedegenerated conjugate to those of the crown gear.

9. A pair of gears comprising a crown gear and a pinion, said pinion meshing with said crown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, both said crown gear andpinion having tooth surfaces curved longitudinally along circular arcs, the tooth surfaces of the pinion being curved along slightly different circular arcs from the mating tooth surfaces of the crown gear, said crown gear having tooth surfaces of straight profile and uniform pressure anglesfrorn end to end, but of different pressure angle on opposite sides, he concave sides of the teeth being of the larger pressure angle and said pinion having tooth surfaces molded-generated conjugate to those of the crown ion having molded-generated tooth surfaces and meshing with said crown gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, the mating tooth surfaces of said gear and pinion havingslightly different lengthwise tooth curvatures.

meshing therewith with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of said crown gear, said crown gear having teeth'which are of different pressure angle on opposite sides,

theconcave sides of'the teeth of the crown gear being of larger pressure angle, and said pinion having. molded-generated tooth surfaces generatedto mesh with those of the crown gear in said offset position but whose lengthwise tooth curvature is slightly different from the lengthwise tooth curvature of mating tooth surfaces of the crown gear.

12. A pair of gears comprising a longitudinally curved tooth crown gear having tooth surfaces of straight profile and of uniform pressure angle from end to end, and a pinion meshing with said gear with its axis offset from the axis of the crown gear and disposed at-right angles to a plane containing the axis of the crown gear, said pinion having longitudinally curved teeth whose tooth surfaces are molded-generated and conjugate to those of the crown gear.

13. A pair of gears comprising a longitudinally curved tooth crown gear having tooth surfaces of straight profile and of uniform pressure angle from end to end but of different pressure angle on opposite sides, and a pinion meshing with said gear with its axis offset from the axis of the crown gear and disposed at right angles to a plane containing the axis of the crown gear, said pinion having longitudinally curved teeth whose tooth surfaces are molded-generated to mesh with those of said crown gear.

' ERNEST WILDHABER.

11. A pair of gears comprising a longitudinally curved tooth, crown gear and a cylindrical pinion lift 

